FR2890487A1 - Electric contact realizing method for e.g. circuit breaker, involves fixing contact pad on contact finger in direction parallel to plane, where contact pad is positioned through insertion in cavity in lateral sides of fingers - Google Patents

Abstract

The method involves fixing a contact pad (2) in composite material on a contact finger (15) in conducting material. A contact zone (40) is cooperated with an electrical contact (50), where the surface is between contact plane (X`, Y`) perpendicular to separation plane (XZ) of contacts. The contact pad is fixed on the finger in the direction parallel to the contact plane. The pad is positioned through insertion in a cavity in lateral sides of the fingers, where the cavity has a base. Independent claims are also included for the following: (1) an electric contact made by implementation of electrical contact forming method (2) a power outage apparatus comprising fixed contact.

Description

METHOD FOR MANUFACTURING AN ELECTRIC CONTACT, ELECTRIC CONTACT

  MANUFACTURED ACCORDING TO SAID METHOD AND ELECTRIC APPARATUS COMPRISING SUCH A CONTACT

  TECHNICAL FIELD OF THE INVENTION [0001] The invention relates to a method for producing an electrical contact comprising a conductive material contact finger on which at least one contact pad made of composite material and a surface or zone is fixed. said contact surface or contact area is included in a plane of contact substantially perpendicular to the contact separation plane. At least one contact pad is fixed on the contact finger in a direction substantially parallel to the contact plane.

STATE OF THE ART

2] The presence of electrical faults in cut-off devices such as circuit breakers, switches or electrical contactors causes their electrical contacts to open abruptly. This rapid opening is generally accompanied by the birth of electric arcs giving rise to significant stresses at said contacts, more particularly at their surfaces or contact areas.

In order to increase the life of the electrical contacts used in such devices, it is known to modify the structure of the surface or contact area of the electrical contacts.

4] It is possible to proceed with the deposition of a single layer of conductive material based in particular on silver. This thin layer of silver a few micrometers thick is mainly used for the purpose of increasing the conductivity at the contacts. Note however that this layer disappears from the first openings of the contacts in the presence of electrical faults.

5] More resistant solutions consist in adding at the surface or contact area composite materials in the form of pellets of different thicknesses and different materials.

6] The pellets are usually made of silver or copper alloy.

  They are made in the usual manner by sintering a powder composed of a silver-based alloy, in particular silver and graphite, silver and metal oxide, silver and tungsten or silver and nickel. For some particular applications, this alloy can be based on copper, especially copper and tungsten or copper and tellurium.

7] The shape of the pellets often corresponds to the final shape of the contact surface of the electrical contact.

8] The pellet is then fixed or attached to a copper support or a copper alloy. The support, in this case the contact finger, generally cut to a predetermined shape in a plate, has a fixing base on which the pad is attached. [0009] Many fixing methods, more or less expensive, are described in particular. in patents FR2541520 and FR2633855. The pellet is usually welded to its support.

0] When the surface or contact area is on the edge of the contact fingers, generally in a plane substantially perpendicular to the contact separation plane, the seating surface useful for fixing the pellet can then be reduced. Indeed, when the thickness of the plates in which the contact fingers are cut are thin, the seating surface is really small. The pellets fixed with conventional solutions can then be subjected to mechanical problems such as the tearing of the contact pads, [0011] Only a few known methods, particularly in the DE1928587 patent, then make it possible to fix the pellets with sufficient pull-out resistance . However, the contacts made with such processes, have a contact surface made exclusively of refractory material which does not facilitate the removal of the arc from the contact zone. This results in greater wear of the refractory material and degradation of the contact resistance faster. This strongly impacts the performance of the devices such as the service life. There is also a greater heating in the area of contact.

2] Finally, the solution as presented in DE1928587 uses a refractory material in the form of a wire. This wire refractory material can be difficult to obtain from an industrial point of view. In addition, the manufacturing process of this solution does not optimize the amount of refractory material used to make the pellet. In addition, the electrical contact between the chip of refractory material and the support may be insufficient.

  SUMMARY OF THE INVENTION The invention therefore aims to remedy the disadvantages of the state of the art, so as to propose a method of manufacturing an electrical contact where the contact pads are firmly and durably fixed.

4] The method of producing an electrical contact according to the invention consists in inserting said at least one contact pad into a cavity in one of the lateral faces of the contact finger, said cavity comprising a bottom.

5] According to a development mode of the invention, the method consists in cutting the contact finger along a predetermined contour in a direction substantially perpendicular to the contact separation plane, and so that at least a portion of the contact pad constitutes a part of the surface or contact area of said electrical contact.

6] In a particular embodiment, two contact pads are each positioned in an independent cavity placed respectively on one of the lateral faces of the contact finger, the bottoms of the two cavities being separated by the conductive material of the contact finger [0017] Advantageously, the two cavities are placed opposite to the lateral faces of the contact finger.

Advantageously, the contact patch is made by sintering a powder composed of a silver alloy.

9] Advantageously, the cutting of the contact finger is performed so as to create a clearance of material at the contact zone, this release of material along the contact separation plane, is delimited by a first straight line passing through the zone. contact and parallel to the axis and a second straight line passing through said zone and forming at least one angle with the first straight line.

0] Advantageously, the contact pad is fixed to the contact finger by welding.

1] An electrical contact made by the implementation of the above-defined device comprises a surface or contact area of the electrical contact consisting of at least a portion of the patch and at least a portion of the contact finger. .

2] Advantageously, the surface or contact area of the electrical contact consists of at least a portion of two contact pads and at least a portion of the contact finger.

3] Preferably, said at least a portion of the contact finger of the surface or contact area is between the two contact pads.

4] In a particular embodiment, the contact finger comprises a clearance of material at the surface or contact area, a material clearance along the contact separation plane delimited by a first straight line passing through the surface or zone contact and parallel to the axis and a second straight line passing through said surface or area and forming at least an angle with the first straight line.

5] An electric power cut-off device comprising at least one fixed contact cooperating, in the closed position, with the surface or contact area of the electrical contact of the above-defined manner, said electrical contact being able to move along the plane of separation of contacts.

BRIEF DESCRIPTION OF THE FIGURES

6] Other advantages and features will emerge more clearly from the following description of a particular embodiment of the invention, given by way of non-limiting example, and represented in the accompanying drawings, in which: FIGS. 5 to 5 represent the main steps of the method of manufacturing an electrical contact according to a first preferred embodiment of the invention; Figures 6 and 7 show two views of an electrical contact according to a first preferred embodiment of the invention; FIGS. 8 and 9 show two views of an electrical contact according to a second preferred embodiment of the invention; Figures 10 and 11 show the electrical contact according to the invention in the open position and closure in a plane parallel to the contact separation plane; FIG. 12 represents an alternative embodiment of the electrical contact according to the various embodiments of the invention; Figures 13 to 17 show alternative embodiments of the contact pads of the electrical contacts according to different embodiments of the invention.

  DETAILED DESCRIPTION OF AN EMBODIMENT

7] According to a first preferred embodiment shown in Figures 1 to 5, the method of manufacturing the electrical contact comprises three main stages taking place chronologically.

8] The support 1 on which will be fixed pad 2, is usually a piece of copper or any other electrically conductive material. The support 1 has a rectangular parallelepipedal overall shape. In the exemplary embodiment, the thickness of the copper support is close to 2 mm, and the width close to 12 mm, but it is clear that the invention is applicable to contacts of different dimensions adapted to the characteristics of the apparatus comprising this contact.

9] The step of fixing the pellet 2 on the support 1 repeats the technical process described in the patent FR2633855 cited here by reference.

In a first step, the support 1 is prepared in order to be able to receive the contact pad 2. The support 1 is placed between a punch and a die of a press, capable of deforming the support 1 to create a location intended to receive the contact pad 2. Following this deformation schematically in Figures 1 and 2, a cavity 3 is then observed on the large upper side surface 4 of the support 1, and a boss 6 on the opposite side face 5. The cavity then comprises a bottom 8. Preferably, the contact pad 2 is intended to bear on said bottom.

1] In the example presented, the punch has a nipple of shape conjugated to that of the cavity 3, this nipple driving the material to appear on the opposite face 5 the boss 6. The deformation of the support 1 having given rise to the cavity 3, is made along an axis Y substantially perpendicular to the large lateral faces 4 and 5 of the support 1.

2] According to this embodiment of the invention, the cavity 3 is made so as not to completely cross the support 1 and the bottom 8 of the cavity 3 has no opening. The cavity 3 is then non-opening.

3] Furthermore, the cavity 3 can also be made by other manufacturing processes such as machining by material removal, hot stamping, hydroforming or electroforming.

4] In the example illustrated in FIG. 1, the following operation consists in introducing, in the direction 30, the contact pad 2 into the cavity 3.

5] The contact pad 2 is made upstream by compression of a powder composed for example of silver and graphite, silver and nickel, silver and tungsten or silver and metal oxide. This compression operation on a separate machine ensures a simple mechanical cohesion of the grains of the powder but does not provide a significant mechanical strength. The shape of the contact patch 2 can be either definitive or temporary. In the second hypothesis, the pellet will then undergo an ultimate deformation during its fixation on the support 1.

6] As shown in Figures 3 and 4, after introduction of the pellet, the cavity 3 is then completely filled by the pellet 2 which forms a projection or protuberance 7 relative to the upper face 4 of the support 1. The contact pad 2 preferably rests on the bottom 8 of the cavity 3. The support 1 is then placed on a welding machine. The welding machine applies pressure on the treated parts 1 and 2 while circulating an electric current ensuring the heating of the parts. An upper electrode has a shape of shape conjugate to that desired for the pellet 2 obtained by conformation, while a lower electrode has for example a pin protruding slightly, capable of ensuring the displacement of the boss 6. In addition, the lower electrode also causes a slight depression of the material promoting the compression of the pellet 2.

In one of the applications of the invention, taken purely by way of concrete illustration, the upper and lower electrodes are of tungsten and the pressure is between 5 and 20 Kg / mm 2 (1 Kg / mm 2 = 98.1 bar). according to the characteristics of the support 1. The intensity of the current must cause a temperature rise of between 700 and 900 degrees Celsius. This intensity is for example close to 18 kiloamperes in the case of a support having a thickness of 2 mm, as described above. The duration of passage of the current, corresponding to this operation, is of the order of one second, and in any case the application of the current must be extremely fast.

8] Concurrently, a direct sintering of the contact pad 2 and the welding of the latter in the cavity 3 of the support 1 are carried out concomitantly. This fixing method makes it possible to obtain a pull-out resistance of the contact patch 2. high. Indeed, the weld zone between the pellet and the support is substantially equal to the entire connection zone between the pellet and the cavity. This connection zone extends from the bottom 8 of the cavity to the top of the edges of said cavity. In addition, this important bonding surface ensures good electrical conduction between the pad and the contact finger and thus allows better control of the contact resistance.

9] When the volume of the pellet introduced into the cavity 3 is sufficient to create the projection 7, it is not essential to push back the boss 6. According to a preferred method of the invention, it is possible to make use of the repression boss 6 to ensure sufficient compression of the pellet 2, but the invention is not limited to this particular method. The quality of the mechanical attachment and the electrical connection of the chip 2 on the support 1 is then very good. Other methods of fixing the pellet on the support can be envisaged such as crimping or riveting processes by brazing or any other electric heating process.

The last step of the method of manufacturing the electrical contact 17 consists in cutting the support 1 according to a predetermined shape. This cut, made in a direction Y substantially perpendicular to the side faces 4 and 5 of said support, provides the final shape of the electrical contact 17.

1] The electrical contact 17 then comprises two main lateral faces 10 and 11 and a set of surfaces defining the wafer 12 of the electrical contact 17. The side faces 10 and 11 of the contact 17 are substantially parallel to the separation plane XZ of the contacts . Said electrical contact 17 is constituted on the one hand by an electric contact finger 15 and on the other hand by a part or the whole of the contact pad 2.

2] As shown in FIG. 7, cutting the support 1 in the direction of the Y axis makes it possible to make at least a portion of the pellet 2 appear on the wafer 12 of the electrical contact 17. This apparent surface of the wafer 2 is a part of the surface or contact area 40. This surface or contact area 40 is intended to be in contact with a surface or contact area of a second electrical contact. As shown in FIG. 10, the surface or contact area 40 is then included in a contact plane X'Y 'which is substantially perpendicular to the separation plane XZ of the contacts.

3] The surface or contact area 40 is therefore composed of at least one silver alloy portion corresponding to the contact pad 2 and a copper portion 20 corresponding to the contact finger 15. This mixed composition allows both to have a surface or contact area resistant to erosion due to the presence of a silver alloy but also a surface or contact area promoting the displacement of the arc through the presence of copper 20 .

4] The electric arc on the contact can interact with two different materials. The presence of the conductive material makes it possible to generate metal vapors which have the effect of reducing the time of presence of the arc on the contacts, in other words the switching time. The refractory material makes it possible to obtain good erosion resistance as well as good resistance over time to the contact resistance. The combination of these effects makes it possible to increase the lifetime of the contact and to reduce its cost.

5] The cutting of the contact finger 15 can use other techniques such as laser cutting, stamping or sawing.

6] According to a second preferred embodiment, the contact finger can receive two contact pads 2a, 2b respectively in two cavities 3. The cavities are preferably placed in a screw facing each other on the large faces 4 and 5 of the contact finger 15. when the cavities are placed opposite each other on the large lateral faces 4 and 5, the respective bottoms 8 of the two cavities are separated by a layer of conductive material contact finger. Moreover, the cavities 3 are made so as not to completely pass through the contact finger 15. The contact pads 2a, 2b are introduced into the cavities 3 as shown in FIG. 10 and then soldered to the contact finger 15. The machine soldering applies pressure to the treated parts 1, 2a and 2b, while circulating an electric current ensuring the heating of the parts. Electrodes have respectively a shape of shape conjugate to that desired for the pellets 2a, 2b obtained by conformation. The electrical contact 17 comprises i0 then two main lateral faces 10 and 11 and a set of surfaces defining the wafer 12 of the electrical contact 17. The surface or contact zone 40 is then composed of two corresponding silver alloy outer parts. two contact pads 2a, 2b and a central portion 20 of copper. This mixed composition makes it possible at the same time to have an erosion resistant contact surface because of the presence of a silver alloy but also a contact surface favoring the displacement of the arc thanks to the presence of copper. 20.

7] According to an alternative embodiment, the pellet placed in the cavity 3, can be flush with the upper face 4 of the support 1 or even be slightly withdrawn. If the cavity 3 is only partially filled by the pellet, an operation of displacement of the boss 6 is then essential.

8] According to one variant, the alloy powder constituting the pellet 2 can be directly introduced into the cavity 3 without being previously shaped by compression. The powder is directly sintered in the cavity 3.

  According to an alternative embodiment, the two contact pads 2a, 2b used may be of different constitutions.

9] According to another embodiment, the cutting of the support 1 makes it possible to obtain electrical contact 17, the contour of which comprises a clearance of material at the level of the surface or zone of contact and along the plane of separation of the contacts XZ. In the closed position of the contacts, as shown in FIG. 10, this clearance of material along the XZ plane is delimited by a first line 60 passing through the contact zone 40 and parallel to the X axis and a second line 70 passing through said zone and forming at least one angle R with the line 60. In the embodiment shown in Figures 12 and 13, the angle R is approximately equal to 45. This clearance allows an accelerated evacuation of the electric arc at the time of opening of the contact when a fault in an electrical switchgear.

0] According to an alternative embodiment as shown in Figure 12, the electrical contact 17 may comprise two surfaces or 40 separate contact areas. Each of the surfaces or contact areas 40 is each constituted by at least a portion of at least one contact pad 2, 2a, 2b and at least a portion of the contact pin 15. This type of electrical contact 17 is preferably for double cutoff devices. The electrical contact then moves in translation along the Z axis. According to alternative embodiments as shown in FIGS. 13 to 17, the shape of the chip is optimized according to the type of application. The method of manufacturing the electrical contact makes it possible to obtain various forms of contact pad contact. Given that the powder constituting the pellet can be sintered directly into the cavity of the contact finger, the shape and size of the cavity make it possible to determine the definitive shape of the contact pad.

2] According to another embodiment, the bottom 8 of the cavity 3 may comprise at least one opening. The surface of said at least one opening is less than the surface of the bottom 8 of the cavity 3.

3] In addition, thanks to the manufacturing method according to the invention, the size of the contact pads can significantly be reduced while maintaining a sufficient attachment. By optimizing the amount of refractory material used, in particular for the production of thin contacts, it is possible to reduce the manufacturing cost of said contacts.

4] The present contact according to the invention is particularly intended for electrical switching devices such as circuit breakers, low voltage electrical switches or contactors. The electrical contact 17 according to the various embodiments of the invention is the movable contact of an electrical switching device. The surface or contact area 40 of said contact 17, included in the contact plane X'Y 'cooperates with a second fixed electrical contact 50 of the breaking device. According to FIGS. 12 and 13, the lateral faces 10 and 11 of the contact 17 are substantially parallel to the separation plane XZ of the contacts. Moreover, in the exemplary embodiment, these faces will be placed symmetrically on either side of the separation plane XZ of the contacts.

Claims (13)

  1. A method of producing an electrical contact (17) comprising: - a contact finger (15) of conductive material on which is fixed at least one contact pad (2, 2a, 2b) of composite material and - a surface or contact zone (40) called to cooperate with a second electrical contact (50), said surface or contact area (40) is included in a contact plane (X'Y ') substantially perpendicular to the separation plane (XZ) contacts (17, 50), - at least one contact pad (2, 2a, 2b) fixed on the contact pin (15) in a direction substantially parallel to the contact plane (X'Y '), characterized in that said at least one contact pad (2, 2a, 2b) is positioned by insertion into a cavity (3) in one of the lateral faces (10, 11) of the contact finger (15), said cavity (3) having a bottom (8).   2. Method according to claim 1 characterized in that it consists in cutting the contact finger (15) in a predetermined outline in a direction (Y) substantially perpendicular to the contact separation plane (XZ), a part of the surface or contact area (40) of said electrical contact (17) consisting of at least a portion of the contact pad (2, 2a, 2b) and at least a portion of the contact finger (15) 3. Method according to one of claims 1 or 2 characterized in that two contact pads (2a, 2b) are each positioned in a cavity (3) independent placed respectively on one of the lateral faces (10, 11) of the finger of contact (15), the respective bottoms of the two cavities being separated by conductive material of the contact finger (15).   4. Method according to one of claims 1 or 2 characterized in that the two cavities (3) are placed opposite to the side faces (10, 11) of the contact finger (15).   5. Method according to any one of the preceding claims, characterized in that the contact pad (2, 2a, 2b) is produced by sintering a powder composed of a silver alloy.   6. Method according to any one of the preceding claims characterized in that the cutting of the contact finger (15) is performed so as to create a release of material at the contact area (40), the release of material following the contact separation plane (XZ) being delimited by a first line (60) passing through the contact area (40) and parallel to the axis (X) and a second line (70) passing through said area and forming at least one angle (f3) with the first straight line (60).   7. Method according to any one of the preceding claims characterized in that the contact pad (2, 2a, 2b) is fixed to the contact finger (15) 1 o by welding.   8. Electrical contact (17) produced by the implementation of the method according to any one of the preceding claims characterized in that the surface or contact area (40) of the electrical contact (17) consists of at least a part of the pellet (2, 2a, 2b) and at least a part of the contact finger (15).   9. Electrical contact according to claim 8 characterized in that the surface or contact area (40) of the electrical contact (17) consists of at least a portion of two contact pads (2a, 2b) and at least a part of the contact finger (15).   10. Electrical contact according to claim 9 characterized in that said at least a portion of the contact finger (15) of the surface or contact area (40) is between the two contact pads (2a, 2b).   11. Electrical contact according to one of claims 8 to 10 characterized in that the contact finger (15) comprises a clearance of material at the surface or contact area (40), a clearance of material along the plane of separation of the contacts (XZ) delimited by a first line (60) passing through the surface or contact area (40) and parallel to the axis (X) and a second line (70) passing through said surface or area and forming at at least one angle (R) with the first straight line (60).   12. Electrical contact made by implementing the method according to any one of claims 1 to 7 characterized in that the contact finger (15) has two surfaces or contact areas (40) each consisting of at least one part of at least one contact pad (2, 2a, 2b) and at least a part of the contact finger (15).   13. Electrical power cut-off device comprising at least one fixed contact (50), characterized in that said fixed contact (50) cooperates, in the closed position, with the surface or contact zone (40) of the electrical contact (17). according to one of claims 8 to 12, said electrical contact (17) being movable along the separation plane (XZ) of the contacts (17, 50).